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Whether you accidentally omitted information or you slipped up when doing subtraction, making errors on your tax return will cause the IRS to take a second look.

"The No. 1 mistake is not putting down the right Social Security numbers, and the second is not doing the right math," said Thomas Cooke, professor of accounting and business law at Georgetown University.

It may be worth hiring a preparer to handle your return or walk you through the process, Cooke said.

"In tough economic times, people may be getting away from professionals," said Cooke. "And as more and more people do their taxes on their own, there will be more mistakes -- both in terms of math errors and the deductions that are taken."

Take the time to double-check everything if you're filling out your own return, and if you decide to use tax software to file, make sure you understand how to use it, Cooke advised.